Right, but reserve requirements are in the order of a few percent, certainly not enough to prevent a bank run, or preventing you from being insolvent when the bonds you're holding went down in value by 20% due to interest rate movements. At the end of the day what you actually care about is whether you have more assets (cash or equity) than liabilities.
Reserves are but one tool in the arsenal and it's also for tightly managing the maximum leverage. If all your assets are not cash-equivalent and they fluctuate in value then there is no maximum leverage that can be guaranteed a priori and there is operational risk.
The bank also had very few chocolate coins (probably none), but that doesn't mean requiring them to hold more of those in their vault would have improved matters.
The problem is that the bank is insolvent; not so much that the bank is out of liquidity.
If they were solvent, someone would lend them the liquidity they need.